Ordnance chambrage and cartridge case



Nov. 30, 1948. R. w. MILLER ETAL ORDNANCE CHAMBRAGE AND CARTRIDGE CASE Filed Dec. 4, 1944 [UK/EJ72 271"- Fa /p17 Waldo Miller Edward Bade? Fuzz/2]] Patented Nov. 30, 1948 ORDNANCE, CHAMBRAGE AND CARTRIDGE CASE RalphWaldo Miller, Topango, and Edward Baden Powell, San Diego, Calif., assignors, by direct and mesne assignments, of, seventy-five per cent to said Powell, Pasadena, Calif., and

twenty-five per cent to said Miller Application December 4, 1944, Serial No. 566,576

6 Claims. 1

This invention relates to the chambrage of ordnance and fire arms, and its primary object is to provide, by improved chambrage design, a higher efficiency with increased projectile velocities and energies without corresponding increase in the maximum pressures which are evolved in the chamber or behind the projectile.

Without going into the detailed underlying reasons, it may be statedin general that the velocity and energy which is imparted to a projectile of a given mass bya powder charge of given composition, depends upon several factors 7 which include the amount of explosive which is burnt behind the projectile, the manner in which the combustion of the powder charge is controlled and also the manner in which resultant gaseous pressure is applied to the projectile.

Maximum permissible pressures are limited not only by existing ordnance structures and strengths but also by the fact that excessive pressures tend to induce uncontrollable detonationof the charge. Ability to burn a large charge of explosive behind a projectile dependslargely on the control of combustion so as to generate gaseous pressure relatively slowly.

With a relatively slow combustion initiated at the breechend of a chamber or cartridge there is a tendency of the pressure developed initially at that point to force a large proportion of unburnt solid explosive forwardly along the chamber and barrel behind the projectile. That action not only tends to excessive wear of the chamber and barrel but also to inefficient use of the explosive energy.

One of the objects of our invention is to overcome the stated difliculties along with others, and, generally, to enable the efficient burning of a relatively larger powder charge behind a given projectile and to apply the resultant kinetic energy of the combustion gases to the projectile mized and the application of gaseous pressure. and

the flow of pressure gas behind the projectile is so controlled as to give the projectile a relative increase in velocity and energy which is greater than the relative increase in the mass of the charge.

In rifle chambrages, or cartridges, of the type at ID in rifle chamber ll.

where the chamber diameter is larger than the bore, we have discovered that the shape of the chamber neck is a factor having unexpected controlling functions. We have discovered that if the chamber neck be made in a venturi conformatfon instead of conical or bottlenecked as in all standard chambers, the difliculties which we have stated are largely overcome and the efliciencies which we have stated are achieved. Using, as an illustration, the standard rifle chambrage, or cartridge case, which is known as the .300 H 8: H magnum we have found that by proper shoulder configuration 'a charge of about 20 above standard can be burned behind the standard grain bullet, without substantial increase in maximum pressures, and with an increase in bullet velocity from about 3000 feet per sec. to approximately 3400 feet per sec., and an increase in bullet energyof about 27 per cent. The following description, taken in connection with the accompanying drawings, explains in detail a preferred and illustrative chamber configuration as applied, for instance, to the standard .300 H 8: H magnum rifle.

In the accompanying drawings:

Fig. 1 is a view showing inelevation cartridge ammunition in accordance with our invention;

Fig. 2 is an enlarged sectional view of the neck portion of such a cartridge, and

Fig. 3 is a similar sectional view of a modified form of the invention.

In Fig. 1 the body of the cartridge case is shown The shoulder which leads from the body to the neck I! is designated generally .by the numeral l3. Neck [2, and bullet I30 are of standard size, the latter being illustrated as the standard diameter .30 caliber bullet. The rifle barrelf l l may either be the standard barrel with'standard rifling, or, as we prefer, the barrel may be free-bored, as shown at I5, for a distance of about 2" from its breech end, with the rifling lands I6 beginning at that forward point.

The case body as here shown has a cylindric external diameter about the same as the maximum diameter of the standard case referred to; andabout the same length. The body, instead of being heavily tapered in its forward part, is preferably almost cylindric up to the shoulder I3, having only a very slight taper (not shown). The substantially full cylindric form up to the shoulder gives the additional charge capacity, and leaves it substantially wholly for the shoulder to form the reduction between the full sized body and the neck. The particular proportionate length and diameter of body here shown are not 3 controlling in my invention; the proportions may be chosen in any case to engender the highest efiiciency; and those shown are merely typical. Figs. 2 and 3 are drawn quite accurately to scale at twice' a'ctual}sizeiofthis typical design of ammunition ior'a .300 magnum riflefwhich of course is necessarily rechambered. The actual 7 Inch, externally Body diameter at shoulder .500 External neck diameter 3340 Bullet diameter -.308

The Wall thickness of the cartridgeca'se, shown somewhat exagge'ratedly in the drawings, is approximately .016 The internal body diameteriis consequently 2468 And the internal neck diameter .308 The difierence between body and neck diameters (either externalor internal) is .160

'llhe'distance by which the base of bullet I30 iSseat'edin'neck i2 is immat'erial'to our inven- "tion; 'but'thespatial relation'of'the base plane [30a of't'he bullet to the shoulder configuration is of some importance. 4

The shoulder configuration as shown, is gen-- created as follows: Taking a point S on the exterior-of thecase'as an'initial point, a line is drawn at an angle of 45to the axis of the case,

"from"thatp'ointS to the'point'N where the line intersects the exterior of neck I2.

The perpendicular lbi-sector A-Bof line SN is then erected and the center point then chosen to"make 'thedistance OS "or 'O-N equal 'to'approxi- "mately 160'.

--of -the shoulder-. The radius of that 'inner section line is either approximately .160 or maybe sli'g'htly more, as it is in the actual ammunition" which we have made and tested. --Inliig.Z'thea'rc 2! is shown extended in dotted lines at 2 la, and that "arc extension 2la intersects the inner surface of neck '12 at approximately-the bullet base vplane l30a. The resulting distance from point N to the plane of [3a is approximately .154 inch.

One characteristic feature of our shoulder fformation is that a relatively abrupt shoulder is formed in'the cham-brage at the point '22 where the internally convex curve-2l meets the inner m chamber wall of thebody. The internal included 135. Another feature isthe continuous internal convexity of the shoulder surface 2! substantially throughout its section in an axial plane ,suchas the plane of the paper in Fig. 2 (preferably acircular are on a radius of the proportionate dimension stated). And a third'feature of the shoulder configuration is that it is not tangent to the neck at-the point N, but is,'in'f ull effect, :the endportion of the contracting intake of a Venturi formation which, if extended, would have its maXimumc onstriction in a.plane which is represented by the dotted line at 23 rearwardly of bullet'face I30a,- and would then open outto "the full diameter of the bullet at the plane of l30a. In the form of Fig. 2, the inner surface of theshoulder formation, being non tangent to 1 the inner surface of the neck, makes 'an angle with the neck surface of more than 180 as measured internally of the cartridge wall. a

In fact the functional performance of our cham brage seems to be very much, if not wholly, 5 -asif"theWnturi formatiWn "of "shoul'de'r l3'were -continued= on to the plane of'the bullet base as illustrated in Fig. 3. In that figure the shoulder 33a is generated in the same manner as in Fig. 2, 'with the curved shoulder carried on forward to 'the plane or 130a, and with a resulting maximum Venturi constriction in the plane indicated at 23. "The-"action isvery much, if not wholly, as if the 'chambr'a'ge were constructed and proportioned as in Fig-S. In fact we have ascertained that if a cartridge case constructed like Fig. 2 is repeatedly re loaded and shot, the neck portion between the transverse plane of 'point N and the plane of Ia becomes quite definitely thickened between the 'wall of the rifle chamber and the inside of the 20 neck so that the inside is similar to the interior configuration shown in Fig. 3,-except thatthe "'rie'ck necessarily sh'ortens to provide for'th'eincreased wall"thickne's's. *Thus the shoulder formatron-tr FFig. 3' is 'include'd' within "our inven- '25"ti0n inits 'broad'er aspects. Theform'of Fig.2

' however -'seems tohave *all' of 'the "functional aidva'ntages of"Fig."3,"aniiin"addition is easier to manufacture.

In*ordnance-which uses no am'inunitionnas'e. '30 our chambrage which is here described "as the interior of "the"'c'asewill' be applied" directly to the ,gun. Inthat instan'ce the'inte1ior"of"case'neck I 2 becomes.- physically" it here is" in iiect "'the"rearwardfor breech"endof the gunbore. "Or, 35 "amounting to thesame'thifig, tvlientlfe'cai'tiidge is in"the"gun"chamber,' the cartridge ca-s'e'maybe considered as"'a"'llrier and; th'usfia's' forming: the walisor the'gun *cnarnb er 'in'cludirigfthe' described shoulder anmnewair of therear-ward portion of 51 0 t e -ore-:=' "ontainingtheprojectile.

We canncesaytnat the "following explanation is the"ultimatelytru'e and full "account-"of "the functions of our chambrage which'lead to its "Hhidrfsti'atd improvement in *efliciency; but "we have come to the following conclusions"as'a'1'e- Stiltofxtelldd'fiofllparatlve t$tS'WhiChWe' have earnedon'betweenstanuard"ammunition'antrour "i'mnrcvedammuniticn. fSta'nda'rd factory ".3'00*H "cf magnum ammunit cn carries a 'bharge'of "152 grainsof- IMRnitrdce11uldsepowder;"while "our "cartridge "is" regularly loaded "with 75 "grains 'dfthdsifie propellant. v It' has been'uemcnstrated by fepated't'sts'tl'lat'with OTlr ammunition there is far less tendency for thefbu'r' r'iing powder to 'follow fcrwarh "after 'ther'proj'ectile and that "prevention believe to be "due largely, if not wholly; to theparticular "angular venturrformation which;"p'romots"the'fiow of gases forward an'd lnh'ib'its the of-" s'olids inn-forward di- 60 'i'e cti'on b'iit' diives ther'n back -aICHlQSidG the ease wall towards "the" reanas the T'gass issue out the c'er'ite'rthrou'g'h'the'elfective ccnstrl'ctionof the Venturi formation. "Theunb'urnt charge is thus hel'd back While thejg'enerate'd l plssul'e caUSeS 5 gas to""flow' forwardly, c'ontro'lled" by" the' Ver'it'i'iri formation; tlie gaseous 'strea'map 'arently contra-t'irlg at the Virtual Venturi 'neck 'in' the plane 23' and then'expan'um to'tl'ie full' diameter of. the bullet at the' bullt' base. I

Due to" the'iiow'control "oi" the Venturi shoulder 'fo r'rl ationitlie"chamberpressures' seem" to initiallybuild upfrn'o're slowly, with the combustion con- "trolled, while 'the proj ectile is firstput a into "motion and gathering speed. To allow the projectile 7 10 gather ihitialsp'ed rreely'weprrer; although it is not at all necessary, to free-bore the rifle bore for a short distance as-we have stated.

The Venturi formation allows the expanding pressure gases to enter the neck and bore with the minimum turbulence and restraint; the gases flow freely in a smooth stream forwardly behind the projectile. Due'to that free flow, devoid of turbulence, there is a relative absence of surging which minimizes the rearward propagation of pressure waves. That wave propagation, in ordinary chambrages, is one of the factors which causes detonation of the c arge and inhibits controlled slow combustion. The relative elimination of wave pressures enables us to burn the larger charge slowly without increasing peak pressures; and results also in longer maintenance of the maximumpressures after they are reached.

The final resulting facts, ascertained from comparative tests, may be briefly summed up as follows.

The substantially increased weight of charge is burned without any substantial increase in peak pressures, and fired in the same firearm gives no substantially measurable increase in peak recoil as compared with the standard ammunition.

The barrel of the firearm using our chambrage heats up in the forward half of the barrel first and most; indicating maximum bore friction at that point, which comes from maximum pressure reached there; while all standard and other chambrages cause maximum heating in the rear quarter of barrel length.

Muzzle velocity of the standard 180 grain bullet is increased from approximately 3000 ft. per sec. to 3400 ft. per sec.; with a resultant increase in energy from 3600'ft. lbs. to 4625 ft. lbs.

The energy increase is approximately 27 plus. The efficiency increase in energy per unit weight of powder, measured by the energy increase over the powder increase, is approximately 7% plus. Similar comparative tests with standard .30-06' U. S. service ammunition have shown energy increases of better than 30%, with efficiency increases up to 11% It will be understood that the dimensional and other specific figures which we give are merely illustrative of the invention as applied to a specific firearm. The invention is applicable to ordnance of all calibres and kinds.

Our invention will also be understood as relating to chambrage, whether or not the chamber is formed directly in the gun or is formed as the bore and a coaxial combustible-charge-receiving walled chamber of larger diameter than the bore, a coaxial annular shoulder surface joining the walls of the chamber and bore, said surface being internally convex in an axial plane and having substantially circular curvature, said surface being non-tangent to both the chamber and bore Walls and the chordal line of the shoulder are running through .its intersections with the chamber and bore walls extending inwardly and forwardly of the barrel axis.

2. A gun barrel as specified in claim 1, in which the radius of curvature of said shoulder surface corresponds substantially to the difference between the diameters of said chamber and bore.

3. A gun barrel as specified in claim 1, in which said chordal line extends at about 45 to the barrel axis.

4. In cased ammunition having a case forming a forward projectile receiving neck and a coaxial propellant containing body chamber of larger diameter than the neck, a coaxial annular shoulder surface joining the walls of the chamber and neck, said surface being internally convex in an axial plane and having substantially circular curvature, said surface being non-tangent to both the chamber and neck walls and the chordal line of the shoulder are running through its intersections with the chamber and bore walls extending inwardly and forwardly of the case axis.

5. A case as specified in claim 4, in which the radius of curvature of said shoulder surface corresponds substantially to the difference between the diameters of said chamber and neck.

6. A case as specified in claim 4, in which said chordal line extends at about 45 to the case axis.

RALPH WALDO MILLER. EDWARD BADEN POWELL.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 286,649 Stewart Oct. 16, 1883 338,192 Rubin Mar. 16, 1886 651,558 Rylands June 12, 1900 692,819 Bissell Feb. 11, 1902 1,062,604 Pedersen May 27, 1913 2,072,671 Foulke Mar. 2, 1937 2,121,796 Helbich June 28, 1938 FOREIGN PATENTS Number Country Date 13,425 Great Britain Nov. 6, 1885 

